Adaptation concept, tissue remodeling, mechanobiology and tissue engineering: a survey

Man’s interest in biomechanics dates back to ancient Greece (Aristotle 384–322 BC) and perhaps even earlier than that, but it is with Leonardo de Vinci (1452–1519), Galileo (1564–1632) and Harvey (1578–1652) that work reveals the importance of mechanics in physiology. For example, in his work relating to blood circulation and which presented the existence of microcirculation, Harvey wrote: “How does the blood manage to traverse the porosities of the flesh on its way from arteries to the vein?” The term Biomechanics, however, did not come into use before 1887 with Benedikt (uber Mathematische Morphologie und Biomechanick). The 1980’s witnessed the birth of new biomechanics with parallel progress in biology, physics and chemistry. Indeed, we stepped into the era of genomics and proteomics about ten years ago, thanks to new technology allowing us to study microstructures or to measure microforces (e.g. confocal microscopy, magnetic bead cytometry, laseroptical tweezers). Comparing the data arising from these new experimental approaches allowed a better understanding of the relation between applied forces, gene or receptor expression, and synthesis of autocrine factors. This new biomechanics (mechanobiology) led to a better grasp of the tissue remodeling principles observed in some pathologies. Remodeling corresponds to the biological dynamics of a tissue. It can be physiological and ensure the stability of tissue homeostasis or it can evolve and lead to pathological modifications. Remodeling induces mobilization in two different tissue components, i.e. cells that constitute tissue, and the extra-cellular matrix. In more complex mechanisms, the influence of local mechanical forces often plays a predominant role. Tissue remodelling combines modifications in cell expression and the possible mobilization of other cell types like inflammatory cells or progenitors. The deregulation of tissue homeostasis that leads to pathological remodeling are chronic phenomena that often result from diseases related to age. The first observations regarding the mechanical adaptation and the structure/strain relation of the tissues were made a long time ago (Meyer, 1866; Wolff, 1892). Indeed, Meyer in a paper on the structure of cancerous bone wrote (1866) “the spongiasa showed a well-motivated architecture which is closely connected with the statics and mechanics of bone.” Culman, a mathematician who was attending the conference, then pointed out that the shape of a cantilver beam in civil engineering was the same as the head